The present invention concerns a sorter for fibrous suspension having a rotationally symmetric screen and an accepts screen space on the screen outlet side which is located radially outside of the rotationally symmetric screen as is known from Patent GB No. 1,492,209. The present invented sorter features a dampening space with a gas pressure cushion in the upper housing area integral with the accepts screen space. The dampening space is specifically intended to dampen the pulsations in the suspension which are caused by the rotor and the rotating sorter elements attached to the rotor. The rotor and rotating sorter elements are arranged within the rotationally symmetric screen, also known as a screen basket, shortly before the head box of a paper machine.
In the sorter of GB No. 1,492,209, to obtain a dampening space within a maximally large cross section, the pulp inlet and the pump outlet have both been arranged at the bottom of the sorter housing. The drain for the overflow or the sorted fraction is located also at the bottom of the housing. In order to avoid excessive hampering of the sorting effect, and to obtain a reasonably acceptable sorting in GB No. 1,492,209, it was necessary to run the pump inlet centrally into the interior of the screen basket. Thus, the drive shaft for the rotor had to be run through the pulp inlet pipe. This design is in and of itself extremely disadvantageous. Further, another drawback remains in that the sorting effect is not satisfactory due to the bottom location of the two connections for the inflow and the draining of the overflow. Attempts have been made to correct this ineffective sorting through specific cross section ratios of the pipelines and/or feed and drain openings. However, these design modifications have proved unsatisfactory.
Accordingly, the problem underlying the invention is to design a sorter having a dampening space and so that the sorting effect will not be adversely affected. A further problem underlying the invention is to, as far as possible, provide a sorter, which at the same time, has an improved dampening performance.